bioenergetics

• What is photosynthesis?

  An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
• What is the equation?

  carbon dioxide + water -(light)> glucose and oxygen

  
  

  CO2 + H2O -(light)>> C6H12O6 + O2
• how does an increase in temperature affect photosynthesis?

  increase in temp, increase in photosynthesis because the number of collisions increases

  this trend continues up to a certain temperature until the enzymes reached their optimal temp, and then start to denature. then the rate of reaction decreases.
• How does light intensity affect the rate of photosynthesis?

  higher light intensity, higher photosynthesis. because more energy is provided.

  but if it goes above a certain intenity, it stops because another factor has reached its limit ie the limiting factor.
• carbon dioxide?

  as CO2 increases, photosynthesis increases because the rate of reaction increases
• chlorophyll?

  a pigment that converts light energy to food. so if chlorophyll levels are reduced eg through a magnesium deficiency, then the rate of photosynthesis will decrease.
• explain a limiting factor

  any of the factors above may become a limiting factor. this is an environmental condition which restricts the rate of photosynthesis no matter how much the other factos have increased.

  this can be seen on a graph as the curve levelling off.
• what are 5 uses of glucose?

  - respiration

  - produce cellulose to strengthen cell walls

  - converted into insoluble starch

  - combined with nitrates

  - produce oils or fat for storage

  
  

  CORNS (cellulose, oils/fat, respiration, nitrates, starch)
• what is respiration

  The process of transferring energy from glucose which goes on in every cell.

  This is exothermic
• Explain aerobic respiration

  - uses oxygen

  - yields the MOST energy

  - most of these reactions occur in the mitochondria

  - glucose is oxidised to release its energy
• what is the equation for aerobic respiration?

  C6H12O6 + O2 --> CO2 + H20

  
  

  glucose + oxygen -> carbon dioxide + water
• what is anaerobic respiration?

  - occurs when there is not enough oxygen

  - does not yield as much energy as aerobic respiration

  - only used as a last resort

  - the oxidation of glucose is incomplete
• what is the equation for this in animals?

  glucose -> lactic acid
• what is the equation for this in plant and yeast cells?

  glucose -> ethanol + carbon dioxide

  (this reaction is used to make bread and alcoholic drinks)
• what three things happen in response to exercise? why?

  - heart rate increases

  - breathing rate increases

  - breath volume increases

  
  

  Because during exercise, more energy is needed for the muscles to contract, so respiration has to occur faster, so the cells need more oxygen supplied to them and more co2 removed, and this is done by the above 3 processes
• what is the byproduct of ANAEROBIC respiration? what does this lead to?

  a byproduct is lactic acid

  this builds up an oxygen debt (because oxygen is needed to break lactic acid down)
• what is oxygen debt?

  the amount of oxygen needed to oxidise lactic acid

  
  

  The amount of extra oxygen needed to react with the acid and remove it from cells

  Blood flowing through the muscles transports the lactic acid TO THE LIVER where it is converted back into GLUCOSE
• what does oxygen debt result in?

  the muscles tiring and not working properly.
• metabolism is?

  the sum of all chemical reactions in the body.

  the energy transferred in the cells by respiration is used in the process of metabolism to make new molecules. these processes are controlled by enzymes.
• 5 examples of metabolic reactions?

  - glucose molecules being converted to starch, glycogen or cellulose by being joined together

  - a glycerol molecule and three molecules of fatty acids forming a lipid molecule

  - glucose and nitrate ions forming amino acids, which are used to form proteins

  - the reactions in respiration

  - urea forming the breakdown of proteins for excretion

  
  

  GUARL

  (glucose conversion, urea forming breakdown of proteins, respiration reactions, lipid molecule being formed, amino acids formed from glucose and nitrates)
• what is respiration

  The process of transferring energy from glucose which goes on in every cell
• Why is yeast used to make bread rise?

  yeast ferments the flour (breaks down sugars in the flour) and respires anaerobically to release CO2 which makes the bread rise